1. Field of the Invention
The present invention relates to a driving apparatus for an image forming apparatus, such as an office machine including a multi-function device, a laser printer, an inkjet printer, and so on, and more particularly, to an image forming machine driving apparatus having a feeding part power-engaging removal device cutting off a force exerted on a driving gear driving a feeding part when a sheet of paper jammed in the feeding part, such as a pickup roller, a feeding roller, a paper discharge roller, and so on, is removed from the feeding part, while the force is not transferred from the paper to the driving gear, thereby preventing the jammed paper from being ripped off or damaged.
2. Description of the Related Art
In general, an image forming apparatus, such as an office machine including an inkjet printer 10 as shown in FIG. 1, includes a paper supply tray or cassette 1 in which a plurality of sheets of paper P are loaded, a pickup roller 2 supplying the paper P loaded in the paper supply cassette 1, a feeding roller 3 feeding the paper P supplied by the pickup roller 2, a printer head 4 mounted on a carrier 14 to form images on the paper P fed by the feeding roller 3, and a paper discharge roller 5 discharging the image-formed paper P outside the inkjet printer 10.
The pickup roller 2 is coupled with a driving gear 6 of a driving motor (not shown) through a plurality of pickup idle gears 20, 21, and 22 and a pickup roller gear 23, and the feeding roller 3 is coupled with the driving gear 6 through a feeding idle gear 11 and a feeding roller gear 16.
As shown in FIGS. 2A and 2B, on one end 17a of a shaft 17 of the feeding roller 3 is installed a one-direction gear part or a spring clutch part 19 which rotates the feeding roller gear 16 without an additional load by not transferring a rotation force of the driving gear 6 to the feeding roller 3 when the driving gear 6 rotates in one direction, for example, in a counterclockwise direction, by the driving motor so that the paper P is picked up by the pickup roller 2, and by transferring the rotation force of the driving gear 6 to the feeding roller 3 when the driving gear 6 rotates in an opposite direction to the one direction, that is, in a clockwise direction, after the paper P reaches the feeding roller 3.
The spring clutch part 19 is provided with a first hub 18a of a bushing 18 fixed to the one end 17a of the shaft 17 of the feeding roller 3, a second hub 16a of the feeding roller gear 16 rotatably installed to the one end 17a of the shaft 17 of the feeding roller 3, and a clutch spring 19a winding around the first and second hubs 18a, 16a to generate a sliding friction force on outer circumferences of the first hub 18a of the bushing 18 and the second hub 16a of the feeding roller gear 16.
As the second hub 16a of the feeding roller gear 16 rotates in a winding direction of the clutch spring 19a, for example, in the clockwise direction by the feeding idle gear 11 subjected to the rotation force of the driving gear 6 (refer to FIG. 2A), the spring clutch part 19 transfers a dynamic power of the second hub 16a of the feeding roller gear 16 to the first hub 18a of the bushing 18 disposed nearby the first hub 16a since the clutch spring 19a comes in tight contact with the outer circumferences of the first and second hubs 18a and 16a while an inner diameter of the clutch spring 19a becomes smaller by the sliding friction force with the first and second hubs 18a and 16a. Consequently, the dynamic power of the driving gear 6 is transferred to the feeding roller 3 through the feeding idle roller 11 and the feeding roller gear 16 to rotate the feeding roller 3, and thus the paper P is conveyed to the printer head 4.
Further, as the second hub 16a of the feeding roller gear 16 rotates in a direction opposite to the winding direction of the clutch spring 19a, that is, in the counterclockwise direction, the spring clutch part 19 rotates the feeding roller gear 16 without the additional load since the clutch spring 19a becomes spaced-apart from the outer circumferences of the first and second hubs 18a and 16a while the inner diameter of the clutch spring 19a becomes larger by the sliding friction force with the first and second hubs 18a and 16a. Accordingly, the dynamic power of the driving gear 6 is cut off between the feeding roller gear 16 and the feeding roller 3 so as not to be transferred to the feeding roller 3.
Even though not shown, on the pickup roller gear 23 formed on the shaft of the pickup roller 2 or one of the pickup idle gears 20, 21, and 22 is mounted another one-direction gear part or another spring clutch (not shown) which transfers the rotation force of the driving gear 6 to the pickup roller 2 as the driving gear 6 rotates in another one direction, for example, in the counterclockwise direction, by the driving motor so that the paper P is picked up by the pickup roller 2, and rotates the pickup roller gear 23 or the pickup idle gears 20, 21, and 22 without the additional load by not transferring the rotation force of the driving gear 6 to the pickup roller 2 as the driving gear 6 rotates in the opposite direction, that is, in the clockwise direction, after the paper P reaches the feeding roller 3.
In operations of the inkjet printer 10 having the above structure, when the inkjet printer 10 starts its operation, electric power is applied to the driving motor, by which the driving gear 6 rotates in the one direction, for example, in the counterclockwise direction, to rotate the pickup roller 2, the feeding roller 3, and the paper discharge roller 5.
At this time, the pickup roller 2 rotates in a direction picking up the paper P, that is, in the counterclockwise direction, by the one direction gear part or the spring clutch part 19.
However, the feeding roller 3 remains in a stationary state since it does not receive the dynamic power of the driving gear 6 by the spring clutch part 19.
That is, when the feeding idle gear 11 receiving the rotation force in the counterclockwise direction of the driving gear 6 rotates in the clockwise direction, the feeding roller gear 16 meshed with the feeding idle gear 11 rotates in the counterclockwise direction. Accordingly, the clutch spring 19a becomes spaced-apart from the outer circumferences of the first and second hubs 18a and 16a while the inner diameter of the clutch spring 19a becomes larger by the sliding friction force with the first and second hubs 18a and 16a, so that the feeding roller gear 16 is rotated in the direction opposite to the winding direction without the additional load. Consequently, the dynamic power of the driving gear 6 is cut off between the feeding roller gear 16 and the feeding roller 3 so as not to be transferred to the feeding roller 3.
Further, the paper discharge roller 5 rotates in a direction opposite to a paper convey direction A through the driving gear 6 and a power transfer gear train not shown.
As described above, as the pickup roller 2 rotates in the counterclockwise direction, the paper P loaded in the paper supply cassette 1 is picked by a friction buckler (not shown) and conveyed to the feeding roller 3.
Thereafter, when an upper end, that is, a leading end, of the paper P pushes a sensor actuator 9 of a paper sensor 7, an optical sensor 8 generates an ‘on’ signal. Accordingly, a controller (not shown) drives the driving motor to rotate the driving gear 6 in the opposite direction, that is, in the clockwise direction.
As the driving gear 6 rotates in the clockwise direction, the transfer of the dynamic power of the driving gear 6 to the pickup roller 2 is cut off by the one direction gear part or the another spring clutch to stop operations of the pickup roller 2. At this time, the dynamic power of the driving gear 6 is transferred to the feeding roller 3 by the spring clutch part 19 to rotate the feeding roller 3 in the paper convey direction A, that is, in the clockwise direction. As a result, the paper P moves to the paper convey direction A and enters between a base frame 12 and the print head 4.
At this time, the paper discharge roller 5 rotates in the paper convey direction, that is, in the clockwise direction through the power transfer gear train.
Thereafter, the controller counts a time period after the optical sensor 8 generates the ‘on’ signal, and generates a print command to eject ink through ink jet nozzles 4a of the printer head 4 if the time period exceeds a predetermined time, that is, if a front end of the paper P passes under ink jet positions of the ink jet nozzles 4a and enters up to a predetermined printing location.
Accordingly, the printer head 4 forms an image by ejecting ink on the paper P, sliding in left and right directions with respect to the paper convey direction the carrier 14 supported by a carrier shaft 15.
As described above, the image-printed paper P is externally discharged by the paper discharge roller 5 and a star wheel 5a. 
However, the conventional inkjet printer 10 has a power transfer/cutoff device, such as the one direction gear part or the spring clutch part 19, mounted to each of the pickup roller 2 and the feeding roller 3, respectively, to transfer or cut off the rotation force of the driving gear 6 to/from the pickup roller 2 and the feeding roller 3 according to the rotation direction of the driving gear 6. Therefore, when the paper P jammed between the pickup roller 2 and the paper supply tray 1 or between the feeding roller 3 and a backup roller 3a due to a skewed supply of the paper P is removed, the pickup roller 2 or the feeding roller 3 rotates in a paper removal direction. The paper removal direction may be not the same as the power transfer direction of the one direction gear part or the spring clutch part 19 mounted to the pickup roller 2 of the feeding roller 3. Accordingly, the jammed paper P is easily removed since the pickup roller 2 or the feeding roller 3 rotates without the additional load by a paper removal force. But, the jammed paper P is not easily removed in the same direction since the paper removal force is reversely transferred to the gear train, such as the feeding idle gear 11, the pickup idle gears 20, 21, and 22, the driving gear 6, or the like.
In more detail, in a case that the paper P is jammed in a state that it nearly moves out between the feeding roller 3 and the backup roller 3a, a user needs to pull out an externally discharged leading end of the paper P in the paper convey direction A in order to remove the jammed paper P from the inkjet printer 10. At this time, the feeding roller 3 rotates in the clockwise direction by the paper P, so the first hub 18a of the bushing 18 of the spring clutch part 19 rotates in the direction opposite to the winding direction of the clutch spring 19a. Consequently, the inner diameter of the clutch spring 19a becomes larger by the sliding friction force with the first and second hubs 18a and 16a, and the clutch spring 19a is spaced-apart from the outer circumferences of the first and second hubs 18a and 16a, so that the feeding roller 6 rotates without the additional load. Accordingly, the user can easily remove the jammed paper P between the feeding roller 3 and the backup roller 3a. 
However, in a case that the paper P is jammed just after the paper P enters between the feeding roller 3 and the backup roller 3a, the user needs to pull out a rear end of the paper P located on a side of the paper supply cassette 1 to remove the jammed paper P. At this time, the feeding roller 3 rotates in the counterclockwise direction by the paper P, so that the first hub 18a of the bushing 18 of the spring clutch part 19 rotates in the winding direction of the clutch spring 19a. As a result, the inner diameter of the clutch spring 19a becomes smaller by the sliding friction force with the first and second hubs 18a and 16a to be in tight contact with the outer circumferences of the first and second hubs 18a and 16a, so that a rotation force of the first hub 18a of the bushing 18 is transferred to the first hub 18a of the adjacent feeding roller gear 16. Accordingly, the rotation force of the feeding roller 3 is transferred to the driving gear 6 through the feeding roller gear 16 and the feeding idle roller 11.
In the above case, the rotation force rotating the driving gear 6 is much stronger than a contact pressure between the feeding roller 3 and the backup roller 3a having the jammed paper P therebetween, so that the jammed paper P slips between and removed from the feeding roller 3 and the backup roller 3a when being pulled out with the rotation force stronger than the contact pressure.
However, at this time, it causes difficulties and inconvenience to remove the jammed paper P since the user must strongly pull out the paper P in order for the jammed paper P to slip between the feeding roller 3 and the backup roller 3a. 
Further, in a case that the jammed paper P is not so strong enough to sustain an exerted force occurring when the user pulls out the paper P for removal, it becomes more difficult to remove the jammed paper P since the paper P is torn off or damaged, thereby causing a problem that a subsequent paper jam occurs.